Key latching and release mechanism



w. R. SMITH 2,720,961

KEY LATCHING AND RELEASE MECHANISM Filed March 51, 1954 INVENTOR. WILLIAM RICHARD SMlTH ATTORNEY United fitates Patent 2,720,961 KEY LATCHING AND RELEASE MECHANISM Application March 31, 1954, Serial No. 420,053 9 Claims. (Cl. 197107) This invention relates to key operated mechanisms and more particularly to program key switches of the type used in business machines.

The function of program keys as used on business machines is described in some detail in a co-pending application, Serial No. 250,647, of C. R. Doty, assigned to the same assignee as that of present invention. But briefly, in a conventional embodiment, a plurality of keys are arranged in side by side relationship and are vertically movable to a latched or unlatched position. Latching is accomplished through the engagement of a notch in the key stem with a bail extending transversely of the axis of all the key stems. Ideally, the depressing of any key moves the bail to release any previously latched key.

In the conventional mechanism, such as that shown in the aforementioned co-pending Doty application, the bail had to be machined to close tolerances and mounted so as to avoid any Warp; otherwise, when moved to its unlatching position, it might fail to release a latched key.

Accordingly, it is an object of this invention to provide an improved release mechanism for latched keys of the subject type.

It is a further object of this invention to provide a key release mechanism wherein the bail warp problem has been eliminated to a considerable extent, thereby permitting the use of an inexpensive latching bail.

It is a further object of this invention to provide an improved mechanism for positively releasing bail latched keys of the subject type.

Other objects of the invention will be pointed out in the following description and claims and illustrated in the ample, the principle of the invention and the best mode, which has been contemplated of applying that principle.

Briefly, this mechanism relates to a cam pivotally positioned on a key stem whereby when the stem is moved in one direction, the cam Wedges a latching bail to an unlatching position, and, when the key stem moves in the opposite direction, the cam is pivoted out of the way by the latching bail.

Referring to the drawings:

Fig. 1 is a perspective view of a plurality of program keys supported for vertical movement to a latched or unlatched position.

Figs. 2, 3 and 4 are side elevations showing the relative positions of the parts of the key operated mechanism during latching and unlatching operations.

In the drawings, a plurality of program keys 2a., 2b, 2c are shown mounted for vertical movement in a U- shaped guide comb 4 which, in turn, is supported by a base member 6 that also carries electrical contacts 8.

Each key 2 comprises a stem 10, key button 12, an insulating block 14, and a contact finger 16 which is to be moved into and out of engagement with one of the contacts 8 to effect an electrical switching operation.

A spring 18 interconnects the upper side of the guide comb 4 with a finger 20 on each key stem 10. This structure biases the key normally to its upper, or unlatched nice position. The limit of the upward movement is reached when the insulating block 14 engages the lower side of guide comb 4.

Formed on the key stem is a shoulder 24 which is engageable by a bail 22 when the key is operated to engage its contact finger 16 with the corresponding contact 8. This inter-engagement, as shown for key 2a in Figs. 1 and 4, prevents spring 18 from biasing the key stem 10 to its unlatched position. In order for bail 22 to effect its latching and unlatching operation, it is pivotally supported at opposite ends by studs 25 (one shown) which pass through suitable bushings or apertures 26 in bail arms 28. The bail is biased by a spring 39 for counterclockwise movement (as viewed in Figs. 2-4) about studs 25 into engagement with all the key stems 10.

If a key is latched in its contact making position, e. g., key 20, Fig. 1 and also Fig. 4, then, in order to release the key, it is necessary to pivot the bail 22 clockwise to a point wherein the shoulder 24 is free of bail 22 where upon spring 13 will lift the key to its unlatched position.

If an inclined surface 34 is provided on the under side or" shoulder 24, then that surface will act as a cam to pivot the bail 22 clockwise when a key is depressed. If the key stems are carefully aligned and if the bail 22 is machined straight, the surface 34 will cam bail 22 clockwise to release any previously latched keys. However, such a careful stern alignment and machined bail has key, the bail pivots about its supporting stud 24 and the cam 36 assume the relative position shown in Fig. 3. position, it will be noted that the bail has been clockwise a considerable extent beyond the nose of the shoulder 24, and this relationship would exist with respect to any other latched key thereby assuring its being released to be pulled to its unlatched position by its spring 18.

With reference again to Fig. 3, it will be noted that when a key stern has been depressed to its contact making or latching position, the point 45 of cam 36 has just passed the bail 22 which is then pulled by its spring 30 into latching engagement with the shoulder 24 of a key stem 10 thereby locking the key in its contact making or latched position. During this movement of bail 22, cam 36 is pivoted counterclockwise to its out of the way position shown in Fig. 4.

In order to achieve this relationship of parts, the point 45 of cam 36 has a maximum radius, with respect to the pivot point 38, which is greater than the distance from the pivot point to the nose of the shoulder 24. When the cam 36 is pivoted clockwise by engagement with the bail 22, as when a key stem 3% is depressed, the point of maximum radius attains a position where 1t extends late ally pivoted the counterclockwise motion of cam 36 (see Fig. 4) so that a portion of the peripheral surface 42 of the cam 36 always extends laterally of its key stem for engagement with the bail 22 where a key is depressed or moved toward its latched position.

Since the extent of throw of the bail 22 is controlled by the point of maximum radius 45 of peripheral surface 42, this dimension is chosen to assure a comfortable clearance between the bail 22 and the nose of the shoulder 24. In one installation, it has been found that if the bail is thrown beyond the shoulder, then previousl latched keys are positively released by depression of another key.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. A key operated mechanism comprising a plurality of keys arranged for parallel movement to a latched or unlatched position, latching means on each key, a bail pivotally mounted for movement transversely of said keys and engageable with said latching means when a key has been moved to its latched position, and means for pivoting said bail to an unlatching position to release any previously latched key comprising a cam pivotally mounted on each key for engagement with said bail, and means on each key for limiting the pivotal motion of its cam whereby when a key is moved toward its latching position its cam acts against said bail to pivot the same to an unlatching position,

2. A key operated mechanism comprising a plurality of keys arranged for parallel movement to a latched or unlatched position, latching means on each key, a bail pivotally mounted for movement transversely of said keys and engageable with said latching means when a key is moved to its latched position, and means for pivoting said bail to an unlatching position to release any previously latched key comprising a cam pivotally mounted on each key with a portion of the cam peripheral surface extending laterally of said key for engagement with said bail, and means on each key for limiting the arcuate motion of its cam whereby when a key is moved toward a latching position its cam acts against said bail to pivot the same to an unlatching position, said cam being so shaped as to permit said bail to engage said latching means after a key has been moved to a latched position.

3. A key operated mechanism comprising a plurality of keys arranged for parallel movement to a latched or unlatched position, latching means on each key, means biasing each key to its unlatched position, a bail pivotally mounted for movement transversely of said keys and engageable with said latching means when a key has been moved to its latched position, and means for pivoting said bail to an unlatching position to release any previously latched key comprising a cam pivotally mounted on each key with a portion of the cam peripheral surface extending laterally of said key for engagement with said bail, and means on each key for limiting the pivotal motion of its cam whereby when a key is moved toward a latching position its cam acts against said bail to pivot the same to an unlatching position, the cam pivot point being so located that said cam is pivotable away from said bail when the key is moved towards its unlatched position.

4. A key operated mechanism comprising a plurality of keys arranged for parallel movement to a latched or unlatched position, latching means on eachkey, means biasing each key to its unlatched position, a bail pivotally mounted for movement transversely of said keys and engageable with said latching means when a key is moved to its latched position, and means for pivoting said bail to an unlatching position to release any previously latched key comprising a cam pivotally mounted on each key for engagement with said bail, and means on each key for limiting the pivotal motion of its cam whereby when a key is moved toward a latching position its cam is wedged against said bail to pivot the same to an unlatching position, said cam being so shaped as to permit said bail to engage said latching means after a key has been moved to a latched position, and the cam pivot point being so located that said cam is pivotable away from said bail when the key is moved towards its unlatched position.

5. A key operated mechanism comprising a plurality of keys each having a stem arranged for parallel movement to a latched or unlatched position, each key stem having a catch thereon, a bail pivotally mounted transversely of said keys to engage a stern catch when a key has been moved to a latching position, and means for pivoting said bail to an unlatching position out of engagement with any stem catch to release any previously latched key comprising a cam pivotally mounted on each key stem with portions of the cam peripheral surface extending laterally of its respective key stem for engagement with said bail, and means limiting the pivotal motion of said cams whereby when a key is moved towards a latching position its cam is wedged against said bail to pivot the same to an unlatching position.

6. A key operated mechanism comprising a plurality of keys each having a stern arranged for parallel movement to a latched or unlatched position, each key stem having a catch thereon, a bail pivotally mounted transversely of said keys to engage a stem catch when a key has been moved to a latching position, and means for pivoting said bail to an unlatching position out of engagement with any stem catch to release any previously latched key comprising a cam pivotally mounted on each key with portions of the cam peripheral surface extending laterally of its respective key stem for engagement with said bail, and means limiting the pivotal motion of said cams whereby when a key is moved towards a latching position its cam is wedged against said bail to pivot the same to an unlatching position, said cam having a maximum radius with respect to its pivot point greater than the distance from said pivot point to said stem catch, said cam pivot point being so located that said point of maximum radius extends laterally from said pivot point a distance greater than said stem catch when said cam has been pivoted into engagement with said bail thereby insuring the pivoting of said bail beyond any stem catch.

7. A key operated mechanism comprising a plurality of keys each having a stern arranged for parallel movement to a latched or unlatched position, each key stem having a catch thereon, a bail pivotally mounted transversely of said keys to engage a stem catch when a key has been moved to a latching position, and means for pivoting said bail to an unlatching position out of engagement with any stem catch to release any previously latched key comprising a cam pivotally mounted on each key with portions of the cam peripheral surface extending laterally of its respective key stem for engagement with said bail, and means limiting the pivotal motion of said cams whereby when a key is moved towards a latching position its cam is wedged against said bail to pivot the same to an unlatching position, said cam having a maximum radius with respect to its pivot point greater than the distance from said pivot point to said stem catch, said cam pivot point being arranged to permit said point of maximum radius to extend laterally from said pivot point a distance less than said stem catch when said cam is pivoted out of engagement with said bail.

8. A key operated mechanism comprising a plurality of keys each having a stern arranged for parallel movement to a latched or unlatched position, each key stern having a catch thereon, a bail pivotally mounted trans versely of said keys to engage a stem catch when a key has been moved to a latching position, and means for pivoting said bail to an unlatching position out of engagement with any stem catch to release any previously latched key comprising a cam pivotally mounted on each key with portions of the cam peripheral surface extending laterally of its respective key stem for engagement with jecting outwardly from one side of each stem and acting as a latching shoulder, means for yieldingly urging each key stem upwardly to its unlatched position, a bail normally engaging said key stems at points below said promember about its pivot by said bail, said cam member operating upon engagement with said limiting means for camming said bail outwardly beyond the end of said projecting portion, said bail then passing over a high per tion of said cam and causing the latter to swing in the opposite direction so as to permit engagement of said bail with said latching shoulder.

References Cited in the file of this patent UNITED STATES PATENTS 2,458,339 Buhler et al. Jan. 4, 1949 

